The present invention relates to a process for the production of expanded clay and shale in a rotary tubular kiln of the type which extends in a straight line without stages and has charging and discharge ends and a burner arranged in the proximity of the discharge end, wherein raw material introduced at the charging end passes through a preheating zone serving for the drying and heating up of the material and is thereupon expanded to the finished product in an expansion zone leading toward the discharge end by means of the heat generated by the burner.
The invention furthermore relates to devices for carrying out such a process in a rotary tubular kiln of the type described above.
In order to manufacture so-called lightweight concrete, use is made of lightweight aggregates which, as is known, particularly include expanded clay and shale, as well as, for example, sintered flue ash. The present invention concerns the production of such lightweight aggregates, primarily expanded clay and shale. Besides serving for the manufacture of lightweight concrete, these aggregates are used occasionally also for other purposes, for example in plant hydroponics, especially for indoor plants. Materials produced according to the present invention are also suitable for these uses.
The conventional processes and apparatus for the production of these lightweight aggregates utilize rotary tubular kilns which represent considerable construction and installation costs and which have an extraordinarily high heat consumption in their operation. The latter factor, in particular, represents an ever-increasing problem in view of the existing scarcity of fuels and the high fuel costs in the relevant industrial area.